Amplifying system



Aug. 4, 1931.

Filed April 11 1928 H L a 4 TN! 5 I J '6 8 I We??? gm 2o Inventor:

Patented Aug. 4, 1931 UNITED STATES PATENT OFFICE -IPAUL D. ANDREWS, OF SCHENECTADY, NEW YORK, ASS IGNOR T0 GJZBTIEIIELAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK AMPLIFYING SYSTEM Application filed. April 11, 1928. Serial No. 269,147.

My present invention relates to amplifying systems and more particularly to systoms of the type in which the. oscillations produced by an electron discharge oscillation generator are amplified by means of a so-called power amplifier.

The object of my invention is to provide 'means for preventing the power amplifier best be understood by reference to the following description taken in connection with a the accompanying drawings in which Figs.

1 and 2 show diagrammatically two different circuit organizations whereby my invention may be carried into effect. I have indicated in both figures of the drawings an amplifying system comprising a grid control electron discharge oscillation generator 1 which generates oscillations which are amplified by means of the grid control electron discharge amplifier 2. The oscillation circuit of the generator 1 comprises three series connected capacities 3, 4 and 5 with a variable inductance 6, for determining the frequency of the oscillations generated, connected in shunt thereto. The oscillation circuit is connected between the grid 7 and anode 8 of the oscillation generator and the cathode 9 is connected to the point 10 between capacities 3 and 4:. The oscillation circuit is connected to the anode 8 through a blocking condenser 11 and power for the operation of the system is supplied from the positive terminal 12 of a suitable source to the anodes 8 and 13 through radio frequency chokes 14: and 15. Amplified oscillations are supplied from the tuned output circuit 16 of amplifier 2 through a coupling transformer 17 to a utilization circuit 18.-

In the arrangement of Fig. 1 the grid 19 of the amplifier 2 is connected through the blocking condenser 20 to the point in the oscillation circuit to which the grid 7 is connected. By means of this connection the oscillations generated by the oscillator 1 are supplied to the grid of the amplifier 2.

Inorder to prevent the amplifier 2 from generating oscillations the anode 13 is connected through a balancing capacity 21 to the point 22 between capacities 4 and 5. If the capacities 3 and 4 are substantially equal and the coupling capacity 21 is made equal to the natural capacity coupling between the output and input circuits of amplifier 2, such for example as the capacity between anode 13 and grid 19 and in some cases other stray capacities, there will be impressed upon the grid by reason of the connection described a potential equal and opposite to that impressed upon the gridthrough the natural capacity coupling andthe tendency to oscillate will be neutralized. This neutralization will be effective at any frequency at which the oscillation generator may be 7 of the plate grid capacity of the power amplifier will also be substantially eliminated and the frequency generated will be independent of any changes in the load-circuit.

The condenser 5 is employed in the anode connection in series with condenser 4 in order to give the desired ratio of plate to grid excitation voltages.

In the arrangement shown in Fig. 2 the circuit is somewhat simplified by reversing the connections of the grid and anode of the power amplifier to the oscillation circuit. This eliminates the necessity of having an extra coupling condenser in the grid connection.

While I have shown and described only two modifications of my invention, it is evident that many Variations in the oscillation,

circuit employed and the circuit connections I d between the oscillation generator and the power amplifier may be made without departing from the scope of my invention as set forthin the appended claims.

What I claim. as new and desire to secure by Letters Patentof the United States is 1. The combination in an amplifying system of an electron discharge grid control amplifier, an oscillation generator having an oscillation circuit comprising an inductance and a plurality of series connected capacities connected between a control grid and an anode, a connection from the grid of the amplifier to a point in said oscilla tion circuit and a connection from the anodeof the amplifier through a coupling capacity to a point in said oscillation circuit separated from the first point by a pair of said capacities.

2. The combination in an amplifying system of an electron discharge grid control! amplifier, an oscillation generator having an oscillation circuit comprising an inductance and a plurality of series connected capacities connected between a control grid and an anode, a connectionfrom the grid of the amplifier to a point in said oscillation circuit and a connection from the anode of the. amplifier through a coupling capacity to a point in said oscillation circuit separated from the firstpoint by a pair of said capacities, the cathode of'the oscillation genenator being connected to a point between said pair of capacities.

3. The combination in an amplifying system of an electron discharge. grid control amplifier, an oscillation generator having an oscillation circuit comprising an inductance and a plurality of" series connected capacities connected between a control grid and an anode, a connection from the grid. of the amplifier to a point in said oscillation circuit and a connection fron the anode of the amplifier through a coupling capacity to a, point in said oscillation circuit separated from the first point by a pair of said capacities having substantially equal values,

the cathode-f the oscillation generator being connected, to a point between said pair of capacities.

l. The combination in an amplifying system of an electron discharge grid control amplifier, an oscillation generator having anoscillation circuit comprising an inductance and a plurality of series connected capacities connected between a control grid; and an anode, a connection from the grid; of the amplifier to a point in said 0scillation circuit and a; connection fromithe anode of the amplifier through a coupling capacity to a point. in, said oscillation circuit separated fronr the first point by a, pair of said capacities, said coupling, capacity being so chosen. with respect to natural. capacity. coupling between the output and input circuits of the amplifier and the relation between said pair of capacities. as to impress upon the grid of; the amplifier a pot-ential substantially equal and oppositeto that im pressed thereon by reasonof the natural ca-. paclty coupling between the output and input circuits of the amplifier.

5. The combination in an amplifying sys tem of an electron discharge grid control amplifier, an oscillation generator having an oscillation circuit comprising an inductance and at least three series connected capacities connected between a control. grid and an anode, a connection from the grid of the amplifier to one point in said oscillation circuit, a connection. from. the anode of the amplifier through a coupling capacity to another point in said oscillation circuit separated: from the first point by a pair only of said capacities and a connection to the cathode of said oscillation generator from a point between said pair of capacities,

6. The combination in an amplifying system off an electron; discharge grid control amplifier, an oscillation generator having an oscillation circuit comprising an inductance and at least three series connected capacities connected between a control grid and an anode, a connection from the grid of the amplifier to one point in said' oscillation circuit, a connection from the anode of the. amplifier through a coupling capacity to another point insaid oscillation circuit separated from. the first point by a pair only of said capacities and a connection to the cathode of saidoscillation generator from a point between said pair of capacities, said coupling capacity being so chosen with respect to natural capacity coupling between the output and input circuits of the ampliher and the relation between said pair of capacities as to impress upon the grid of the amplifier a potential substantially equal and opposite tothati impressed thereon by reason of the natural capacity coupling between the output and input circuits of' the amplifier.

In witness whereof, I have hereunto setmy hand this th day of April, 1928.

PAUL D. ANDRElVS. 

